Terschelling is a municipality and an island in the Wadden Sea (northern Netherlands), one of the West Frisian Islands.
The Wadden Sea is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern continental Europe and the range of Frisian Islands, forming a shallow body of water with tidal flats and wetlands.
The Wadden Sea is the world’s largest area of connected intertidal flats, has existed for several thousand years, despite a more or less steady rise of the sea level. This has been compensated for by transport of sediments into the Wadden Sea from the adjacent offshore waters of the North Sea. There is an ongoing scientific debate about the mechanisms which cause this onshore sediment transport.